Binocular tube assemblies for stereomicroscopes wherein optical beams are folded are, for example, utilized in surgical microscopes. There, the shortest possible working distance between the viewing end of the microscope and the object to be viewed is necessary for large focal intercepts of the main objective. This is necessary in order that the surgeon can assume a relaxed body position during surgery.
It is furthermore desirable in surgical microscopes to provide the possibility of a continuous change off the viewing angle between the housing of the stereomicroscope and the binocular tube assembly. Also, such a binocular tube assembly should provide for adjusting the eye spacing.
A binocular tube assembly which basically satisfies these requirements is disclosed, for example, in U.S. Pat. No. 4,175,286. The binocular tube assembly described here is mounted to be rotatable about a pivot axis disposed perpendicularly to the optical axis of the stereoscopic component beam paths. A deflecting mirror is likewise mounted to be rotatable about the pivot axis. When the binocular tube assembly is pivoted, the deflecting mirror is entrained to rotate therewith by half the pivot angle. A first group off optical deflecting elements follows the rotatable deflecting mirror. This first group deflects the component beam paths coming from the deflecting mirror in the direction of a second group of deflecting elements. Both deflecting element groups can be pivoted together with the binocular tube assembly. Furthermore, and after the second group of deflecting elements, rhombic prisms are arranged in the stereoscopic component beam paths so as to be rotatable about the particular optical axis in order to permit a selective adjustment of the eye distance. The oculars are, in turn, mounted in the component beam paths after the rhombic prisms.
The desire for an ergonomically more favorable pivot range than is realizable with a binocular tube assembly of this kind has resulted, inter alia, in increasing requirements on the work ergonomics. At times, another relative orientation of the binocular tube assembly to the housing of the stereomicroscope is also sought.
The binocular tube assembly disclosed in U.S. Pat. No. 4,175,826 includes an optic component which comprises a prism group having lenses cemented to each end. Such an optical component imposes high requirements with respect to manufacture.
A further binocular tube assembly for a stereomicroscope is disclosed in U.S. Pat. No. 4,798,451. The optical image deflecting elements utilized in this binocular tube assembly comprise mirror-prism combinations which are similar to the beam path trace of portoprisms of the second order. These portoprisms, however, require considerable space and overall lead to a correspondingly wide configuration of the entire binocular tube assembly which sometimes is disturbing to the viewer. Furthermore, relatively long glass and air paths result for an assembly of this kind. Finally, separate deflecting elements in the form of separate pivot mirrors are provided for corresponding ones of the stereoscopic component beam paths. The pivot mirrors therefore also have to be separately adjusted. A very considerable effort for adjustment is therefore necessary.
Furthermore, two component lenses are required in each of the stereoscopic component beam paths in the above-described binocular tube assembly. This, in turn, leads to a very disadvantageous position of the pupils.
A further variation of the binocular tube assembly of the kind described above for stereomicroscopes is disclosed in German published utility registration G 9,308,044.1. The image reversal is here made with the portoprisms of the second order. These optical image reversal elements are very voluminous for large pupil diameters and correspondingly large intermediate images. Also, the possibility of adjustment for the required variable pupil distance with a binocular tube assembly of the kind described in this publication is most complex and can hardly be realized.